The invention relates to a computer aided design method and apparatus comprising means for automatically generating pin-to-pin interconnection lists between respective discrete electrical component circuits. An example of a computer aided design/assembly package is the RACAL REDAC Mini/Maxi PCB Design System, described in the Data Preparation Manual by the Technical Writing Group from the manufacturer, RACAL REDAC Ltd., Newton, Tewkesbury, Gloucestershire, GL 20 8HE, England.